Phenolphthalein Paper by Precision Laboratories. Very sensitive to ammonia vapors and thus is used to detect Ammonia leaks, for example, in refrigerators or air conditioners. Phenolphthalein detects Ammonia in solution from 3 – 5ppm. The test strip will turn a pinkish color if Ammonia is detected. Colour change. pH 8.2 (colourless) to 10.0 (pink).

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